How to test my own nootropics for accuracy?

It depends on the specific product and how much you want to know about it. Let's take adrafinil for example. For that you need to ID with NMR. You could use FTIR if you have a comprehensive enough library of spectra, but the polymorphs of adrafinil can make their IR absorbance shift a lot. So we NMR and FTIR every batch of adrafinil for 100% confirmation of structural identity. NMR is going to cost you a couple hundred bucks per test if you are capable of analyzing it. It's VERY difficult to analyze, though. So you will likely need someone from the lab to analyze it. That's another couple hundred bucks for analyst time. So for you, it would likely be around $400 for a full NMR and analysis.

So now you know that what you have is adrafinil. NMR can pick up hydrogen signals, so you can see other things in there with hydrogens. If it was relatively pure, you might have a couple other signals in there that you can explain. However, you need to assay it for purity. That's where HPLC comes in. Pretty much no labs in the US offer HPLC testing for adrafinil, as you have to design your own methods and get reference standards that likely won't be used too much. So it is going to cost you a lot for HPLC from most labs. It depends on if you can convince them to eat some of the development and reference standard cost or not. If not, you are looking at a few grand for the test at a minimum. If they already had the reference standard and validated methods, they would likely only charge around $300 for the test.

So let's say you talked them into testing it on their HPLC. Now you have assay data compared to a reference standard. Well HPLC is usually done with a UV detector. UV detectors can only detect things with chromophores, or double bonded ring structures. So the HPLC can't see some things, and certain things have much lower limits that you want to have, like heavy metals. So you need to do an ICP-MS for heavy metals. Luckily those methods are pretty standard. So you don't have to pay for any development work. They will likely charge you around $200 for an ICP-MS to check for heavy metals.

So now you have ID, assay, and heavy metals values. If you really want to make sure nothing dangerous is in there, then you have to also test for residual solvents. Synthetic compounds like these use many different volatile solvents in their synthesis. The final purification steps should remove them, but they are not always done right. So you need to use a GC-FID to test for residual solvents. It has to have a headspace autosampler on it for the residual solvent testing, and the lab has to have methods developed for it. Some do, but many don't. If you find a lab that does, it will likely run about $350 per test.

So then you have ID, assay, heavy metals, and residual solvents. What about microbial contamination? Well you need to measure that to ensure there are no harmful microbes. Most of the time that is done with a culture test. They sample it the raw material then culture a plate with agar to see what grows. After a few days they can quantify what does. This determines if the microbial counts are below specs. This test takes a few days, and likely will cost around $150.

There are a couple other tests that are done, like loss on drying. However, those are usually done on assay. That's why you sometimes see an "as is" reading and a "dry basis." As is means they ran the assay as the raw material is, whereas dry basis means they did a loos on drying analysis to determine the water content. Most things have water content specs that you should be under. Loss on drying measures that. Then you also can have melting point analyses or optical rotation measurements using a polarimeter. Most labs don't really use melting point, and adrafinil is always racemic. So you never really see a difference in optical rotation. That would more come into play with amino acids like L-tyrosine or L-theanine.